Whence Australia: Its Precambrian drift history and paleogeography

Abstract

The current shape of Australia is largely an artifact of the previous supercontinent, Pangea. The Great Australian Bight to the south was shaped by Australia and Antarctica breaking apart roughly 90 million years ago, and New Zealand drifting away about 10 million years later, forming the eastern coast of the continent. Nevertheless, Australia has some of the oldest geological material found on the planet, recording over 4.4 billion years of Earth's history. Two-thirds of the western part of Australia is composed of Precambrian rocks, which can broadly be categorized into three cratonic regions, the West Australian, North Australian, and South Australian cratons. These cratons are made up of Archean nuclei that are separated by Proterozoic orogenic belts. The Precambrian paleogeographic drift history of Australia can be subdivided into several main phases, a first phase of independent drifting of the Archean cratons potentially as part of different supercratons Zimgarn (Yilgarn) and Superia (Pilbara) until c. 1.8 Ga, when proto-Australia was likely assembled, a second phase, where the continent occupied an integral position in the supercontinent Nuna between c. 1.6 and 1.2 Ga, moving together with the rest of Nuna in a counterclockwise direction at a paleolatitude of about 30°N, during the third phase, following the breakup of Nuna between c. 1.3 and 1.2 Ga Australia migrated rapidly over the north pole until it returned to another stable position during phase 4 at c. 1.0 Ga during the assembly and tenure of the supercontinent Rodinia of which it remained an integral part. Finally, during and after the breakup of Rodinia, Australia moved again slowly in a counterclockwise direction until the end of the Precambrian.